Electro-pneumatic apparatus for controlling the braking of a railway vehicle

Abstract

The apparatus comprises a sensor for generating a vehicle load signal, weighting devices designed to supply a weighted pneumatic pressure as a function of the load signal, and first and second braking control apparatus, both coupled to the weighting devices and comprising respective relay valves which supply at their outlets respective braking pressures, modulated as a function of said weighted pneumatic pressure, to respective braking actuators associated with the wheels of a respective axle or of a respective bogie of the vehicle. The weighting devices comprise an electro-pneumatic drive assembly which is interposed between pneumatic pressure supply means and the drive inlet of the relay valves and an electronic weighting control unit which controls the drive assembly as a function of the load signal, so as to modulate in a predetermined way the pressure at the drive inlet of the relay valves.

The invention claimed is: 
     
       1. Electro-pneumatic apparatus for controlling the braking of a bogie of a railway vehicle, comprising
 means for generating a vehicle load signal, 
 weighting means designed to supply a weighted pneumatic pressure as a function of the load signal, and 
 first and second braking control means both coupled to the weighting means and comprising respective relay valves which supply at their outlets respective braking pressures, modulated as a function of said weighted pneumatic pressure, to respective braking actuators associated with the wheels of a respective axle or of a respective bogie of the vehicle; 
 the weighting means comprising an electro-pneumatic drive assembly which is interposed between pneumatic pressure supply means and the drive inlet of the relay valves and an electronic weighting control unit which controls said drive assembly as a function of said load signal, so as to modulate in a predetermined way the pressure at the drive inlet of said relay valves; and 
 wherein said pneumatic pressure supply means comprise 
 first and second pressure reservoirs coupled to the inlet of the relay valve of the first and second braking control means, respectively, through respective shut-off valves. 
 
     
     
       2. Electro-pneumatic apparatus according to  claim 1 , wherein the outlets of said shut-off valves are coupled to a maximum pressure selector valve, the outlet of which is coupled to the inlet of said electro-pneumatic drive assembly. 
     
     
       3. Electro-pneumatic apparatus according to  claim 1 , wherein said electro-pneumatic drive assembly comprises a solenoid charging valve and a solenoid discharge valve adapted to cause a pressure increase and a pressure reduction, respectively, in a memory reservoir, the outlet of which is coupled to the first and second braking control means and the inlet of which is coupled to said pneumatic pressure supply means through a pressure limiting valve. 
     
     
       4. Electro-pneumatic apparatus according to  claim 3 , wherein said pressure limiting valve is designed so that the pressure stored in said memory reservoir is always greater than 50% of the braking pressure specified for a crush load condition. 
     
     
       5. Apparatus according to  claim 3 , for a railway vehicle for passenger transport, wherein said pressure limiting valve is designed so that the pressure stored in said memory reservoir is always at least equal to the braking pressure corresponding to the tare braking pressure of the vehicle. 
     
     
       6. Apparatus according to  claim 4 , wherein the outlet of the solenoid discharge valve of the electro-pneumatic drive assembly is coupled to a calibrated orifice, adapted to impede the evacuation of the memory reservoir if said solenoid discharge valve is jammed in the condition in which the pressure is discharged to the atmosphere.